74 



NA TURE 



\Nov. 25. 1880 



pronounce finally upon the prospects of this process," he 

 says (p. 158), " we shall not find this quite an easy task. 

 A few years ago English alkali-makers had such a higli 

 opinion of that process that no new vitriol chambers were 

 built, and the question was discussed whether it was more 

 worth while to work down the existing chambers, or to 

 defray the cost of the new plant at once. Afterwards a 

 less sanguine opinion gained ground, and it seemed as if 

 Hargreaves's process would again be put into the back- 

 ground." At the present moment the writer beheves that 

 the outlook for the Hargreaves process is more favourable 

 than ever. 



Chapters V. and XII., on the Cost of producing Sulphate 

 and Soda-ash, can only serve to give an approximate idea 

 of the matter. The exact cost involved is not readily 

 imparted by manufacturers, and is moreover governed 

 by local circumstances, such as the current price of 

 labour, &c. 



The latter half of the volume is concerned with the 

 second stage in the manufacture of alkali known as the 

 black ash process. In this the salt-cake is heated with 

 limestone and coal, the resulting carbonate of soda being 

 removed_by lixiviation from the insoluble alkah makers' 

 waste. The first part of the chapter on Hand Furnaces 

 appears to be very complete, and the figures on the plate 

 facing p. 3S6 are correct and well-drawn. This can 

 hardly be said of that portion relating to the modern 

 revolving furnaces, this is probably the weakest part of 

 the book, the author having apparently had no practical 

 experience on this point. Figures of two revolvers are 

 given ; of these Fig. 1S2 may be said to represent a fairly 

 good design, though one single wide evaporating pan is 

 considered more convenient for repairs than two narrow 

 ones. As regards the speed of revolution (p. 411) Dr. 

 Lunge is a little out. He says the revolver gearing must 

 be capable of giving speeds of one revolution in four 

 minutes to five revolutions in one minute, "usually the 

 highest velocity does not exceed one revolution per 

 minute." Those figures are not correct for the present 

 style of working. Revolvers should be able to go a good 

 deal slower, but speeds as high as seven to eight revolu- 

 tions per minute should always be possible, especially 

 when working the Pechiney-Weldon process, when the 

 after charge has to be very well and rapidly mixed through 

 the rest. This can hardly be obtained when the large 

 spin-wheel on the revolver is worked from a worm-wheel 

 as Dr. Lunge describes, a pinion-wheel should be used. 

 The author (p. 406) says, " Leaving aside the older con- 

 structions of revolving furnaces, we shall only describe 

 two of the most modern." The first of these has been 

 spoken of above ; the second, figured pp. 414 and 415, a 

 revolver fired by gas, was erected at one works only in 

 1870, and was found to be a failure ; after running a year 

 or two it was entirely reconstructed to burn fuel. Since 

 then the mechanical bogies and engine gearing have 

 been completely altered, so that the figures can hardly 

 be said to represent one of the "most modern con- 

 structions." 



Regarding chimney power Dr. Lunge says (p. 412) that 

 usually every two revolvers have a chimney 6 feet diameter 

 and 100 feet high to themselves. This is certainly not suffi- 

 cient for the most economical working ; to stint a revolver 

 of draught is a serious mistake. 



On another point in the black-ash process Dr. Lunge's 

 opinions do not tally with those of Lancashire manufac- 

 turers. A few years ago Mr. Mactear of St. Rollox pro- 

 posed a plan of adding from 6 to 10 per cent, of lime to 

 the black-ash in excess of that usually worked. This 

 apparently simple process was believed by some likely 

 to work wonders, and statements were made as to the 

 actual gain of many thousands of pounds per annum in 

 a single works by its adoption. Dr. Lunge gives more 

 credit to this than some of our Lancashire friends seem 

 inchned to do. 



The remaining processes in the great suite of chemical 

 changes involved in the alkali trade are as thoroughly 

 discussed by Dr. Lunge as those which have now been 

 noticed. Divergent views concerning many details of 

 these may doubtless be held by various manufacturers, 

 but all will agree in the opinion not only that this is an 

 excellent book, but that it would be very difficult for any 

 one to write a better one. 



H. E. RoscOE 



THE FLORA OF PLYMOUTH 

 Flora of Plynioitth : an Account of the Floivcrijtg Plajits 

 and Ferns found within T-wclve Miles of the Town, 

 with Brief Sketches of the Topography, Geology, and 

 Climate of the Area and History of Local Botanical 

 Investigation. By T. R. Archer Briggs, F.L. S. With 

 Map. 8vo, pp. XXXV. and 432. (London : Van Voorst, 

 iSSo.) 



THIS is a model local flora. Mr. Briggs is well known 

 as one of the most experienced and trustworthy 

 amongst the botanists who have made a special study of 

 British Phanerogamia. He has established a claim upon 

 the gratitude of his fellow-workers by acting for several 

 years as the honorary distributor of their Exchange Club, 

 and in this capacity has received and sent out many 

 thousands of specimens. The present work is the result 

 of the rambles of twenty years, and as he has restricted 

 its limits to a radius of twelve miles from the town, the 

 whole of the district has been within walking distance of 

 his home, and it is probable that there is no tract in 

 Britain of which the plants have been worked out and 

 placed on record in such a thorough and exhaustive 

 manner. A radius of twelve miles from Plymouth 

 includes a great variety of soil and situation. There are 

 the maritime plants of the seashore and the tidal reaches 

 of the Tamar and its affluents. Inland there are in the 

 low country besides the stream-sides, meadows, and culti- 

 vated fields, plenty of woods and deep shady lanes with 

 high banks and thick hedgerows, and the twelve miles 

 radius reaches to a height of 1,700 feet on Dartmoor, and 

 includes a considerable space of open uncultivated heathy 

 and swampy ground. The district is not rich in lime- 

 stone nor in ponds, but except in the plants which afiect 

 these two kinds of station there is full scope so far 

 as situation goes to suit all their varied requirements in 

 habitat. 



Out of the ],68o species enumerated in the last edition 

 of the London Catalogue 873, or considerably more than 

 half, are found within the radius covered by this book. 

 Out of these 728 are natives, and the other 145 more or 

 less certainly introduced by human agency. 



